1. Field of the Invention
This invention relates to the pyrolysis of hydrofluorocarbons or hydrochlorofluorocarbons.
2. Description of Related Art
Indian Patent Publication 158251 (1982) discloses the disadvantage of pyrolyzing chlorodifluoromethane (HCFC-22) to tetrafluoroethylene (TFE) in a platinum tube, namely of providing low conversion and the formation of corrosive products, such as HCI, and alleges to solve this problem by using a reactor tube consisting of nickel or a nickel alloy, after first preheating the HCFC-22 in the presence of copper to scavenge water vapor and form copper oxide. The Publication does not disclose any data to show the improvement over platinum. Moreover, the use of a nickel or nickel alloy tube cannot prevent the formation of HCI because the effect of pyrolyzing HCFC-22 (CF2HCI) is to cause the HCI to split off from the HCFC-22, leaving the :CF2 radical (carbene). The carbenes couple, forming TFE. It is apparent that the reference to a platinum reactor tube in the Publication is a reference to a small research pyrolysis tube, because the expense of platinum has lead the industry away from using this material in a commercial-size reactor. The same is true for nickel, not because of an expense issue, but because nickel lacks the strength and ductility for fabrication into a commercial-size reactor. Nickel alloy, notably Inconel® alloys containing 13–25 wt % Cr, with Mo and other metals, have been the industry standard material of construction for furnaces for the pyrolysis of hydrochlorofluorocarbons or hydrofluorocarbons to fluoromonomers such as TFE, such alloys having sufficient strength and ductility for fabrication and corrosion resistance under pyrolysis conditions to be useful in this application.